Scalable synthesis of KNaTiO3-based high-temperature CO2 capture material from high titanium slag: CO2 uptake, kinetics, regenerability and mechanism study

Abstract

KNaTiO3 is a novel type of solid CO2 sorbents with strong sorption capacity and excellent regenerability at high temperatures. However, the expensive titanium precursor hampers its implementation for industrial applications. Herein, advanced KNaTiO3 based CO2 sorbents were first fabricated directly from high titanate slag (HTS). Elemental mapping analysis reveals high dispersion of KNaTiO3 and the crystal structure of KNaTiO3 in KNaTiO3-HTS-3 almost unchanged even after 15 cycles. The carbonation conversion of KNaTiO3-HTS-3 preserved a highly commendable value even after 100 sorption/desorption cycles, outperforming pure KNaTiO3. In addition, this sorbent exhibited faster sorption rate at 700 °C. Dynamic simulation demonstrated that the sorption constants k1 and k2 are higher and the activation energy is lower than those of conventional high-temperature sorbents. The CO2 sorption capacity of KNaTiO3-HTS-3 only met a slight decrease from 15.7 to 14.6 wt% with the decreasing CO2 concentration from 100 to 10 vol%. Compared with traditional high temperature CO2 sorbents, KNaTiO3-HTS-3 shows a slower breakthrough time. The reaction mechanism process for the promising sorbent is proposed. The HTS-derived KNaTiO3-based high-temperature CO2 sorbent has outstanding CO2 uptake, excellent regenerability, fast reaction kinetics as well as low cost, offering bright prospects in practical applications.